Added UMA stats to overview mode

ash/wm/window_cycle_controller.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ASH_WM_WINDOW_CYCLE_CONTROLLER_H_
 #define ASH_WM_WINDOW_CYCLE_CONTROLLER_H_
 
 #include "ash/ash_export.h"
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/time/time.h"
 
 namespace ui {
 class EventHandler;
 }
 
 namespace ash {
 
 class WindowCycleList;
 
 // Controls cycling through windows with the keyboard via alt-tab.
@@ skipping 37 matching lines @@
 
  private:
   // Cycles to the next or previous window based on |direction|.
   void Step(Direction direction);
 
   scoped_ptr<WindowCycleList> window_cycle_list_;
 
   // Event handler to watch for release of alt key.
   scoped_ptr<ui::EventHandler> event_handler_;
 
+  base::Time cycle_start_time_;
+
   DISALLOW_COPY_AND_ASSIGN(WindowCycleController);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_WINDOW_CYCLE_CONTROLLER_H_